The perpendicular magnetic recording system is a suitable system for improving the areal recording density because, in consequence of causing the easy axis of magnetization of the magnetic recording layer heretofore laid in the in-plane direction of the medium to lie in the vertical direction of the medium instead, the demagnetizing field in the neighborhood of the magnetization transitional region constituting the boundary between adjacent recording bits is decreased and therefore the magnetostatic stability is increased and the resistance to thermal fluctuation is enhanced in accordance as the recording density is heightened.
When a soft under layer made of a soft magnetic material is interposed between a substrate and a perpendicular magnetic recording film, the resultant product is capable of functioning as a so-called vertical two-layer medium and acquiring a high recording ability. In this case, the soft magnetic soft under layer is fulfilling the role of refluxing the recording magnetic field from the magnetic head and is enabled to enhance the recording and reproducing efficiency.
Generally, as under films, various kinds of materials have been proposed. For example, Ti alloys (refer to Japanese Patent No. 2669529, for example), Ni—Fe—Cr alloys (refer to WP-A 2003-123239, for example), etc. having an hcp or fcc structure and Ta or other elements having an amorphous structure may be cited.
Since the under film is a governing element that determines the particle diameters and orientations of the intermediate layer and magnetic recording layer stacked thereon, the selection of the material therefore proves to be very important in order to determine the recording and reproducing characteristics of the magnetic recording medium.
The interposition of the under film between the soft under layer and the magnetic layer results in causing the distance between the magnetic head and the surface of the soft under layer to be increased by the thickness of the under film. For the purpose of enabling the writing to be made fully satisfactorily, therefore, the necessity arises that the soft under layer be given an adequate thickness. Since the under film uses a material possessing a soft magnetic property, however, it is enabled to fulfill the role of a soft under layer and control the crystal orientation of the intermediate layer disposed thereon.
The structure of medium proposed heretofore is not sufficient to obtain a magnetic recording medium excelling in the recording and reproducing property. Thus, the desirability of a magnetic recording medium that solves this problem and allows easy manufacture as well has been finding recognition.
This invention has been proposed in view of the state of affairs and is aimed at optimizing the material for the under film and thereby providing a magnetic recording medium and a magnetic recording and reproducing device excellent in productivity and capable of recording and reproducing information of high density.
For the purpose of accomplishing the object mentioned above, this invention has adopted the following configurations.